This invention relates to semiconductor materials. More particularly, it is concerned with methods of expitaxially growing one semiconductor material on a substrate of a different semiconductor material.
The heteroepitaxial growth of gallium arsenide directly on silicon substrates is desirable for the monolithic integration of gallium arsenide and silicon device technologies, and for the fabrication of high efficiency light-emitting diodes and solar cells on relatively low cost and high purity silicon substrates. Gallium arsenide has been grown expitaxially on silicon substrates by employing molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE) techniques. These processes, however, require heating of the silicon substrates to high temperatures, of the order of 850.degree. C. or more, prior to the deposition procedure in order to produce device quality gallium arsenide epitaxial layers. These temperatures may be detrimental to device structures previously fabricated within the silicon substrates. In addition, the large thermal expansion and lattice mismatches between gallium arsenide and silicon are likely to cause stress and dislocations in the epitaxial layer and thus impose restrictions on the thickness of the layer.